It is known to drive the workpiece spindle of tool machines through a worm for the purpose of overcoming play (backlash), the pitch of which worm changes from the one end to the other end. The amount of play is determined by axially moving this worm and by axially securing same if freedom of play is found. These worms are very expensive and a complete freedom of play cannot be achieved, because heat expansion, pitch errors and other influences must be considered.
It is also known to drive the spindle through two worms, which are moved against one another for a freedom of play so that each one worm engages both flanks of the worm gear. A residual amount of play remains either in existence or the drive jams up for reasons of heat expansion, pitch inexactnesses and other influences.
Finally it is also known to drive playfree with two worms, of which one worm can give way axially against a force. This device is little effective. Furthermore, the two last-mentioned arrangements are expensive.
The basic purpose of the invention is an as inexpensive as possible drive mechanism, in which the freedom or lack of play is assured better than in the known devices. Furthermore, a damping of the rotary oscillations is supposed to be achieved.
The basic purpose of the invention is attained by a drive mechanism, which has the characteristics of the first patent claim. The term brake includes in the sense of the invention also all rotary oscillation dampers and cancellers and driven plates.
The effect of the invention is based namely on the high speed translation at the slack absorbing worm. If this translation would be small, then the rotation based on nonuniformity, which is to be avoided would not arrive at the brake, because of the elasticity of the system. However, due to the high speed translation, at a very small angle of rotation at the spindle there results a very large angle at the brake. The limit of the translation is the automatic locking wherein one must start out from the static friction condition. Due to the fact that the towing worm lies very closely beside but outside the automatic locking area, also already through this a rebound is avoided.
Further advantages and characteristics of the invention result from the following description.